1. Field of the Invention
The present invention relates to an outrigger device to be installed on a wheel-mounted working machine, such as a truck crane, rough terrain crane, or wheel shovel and more particularly it relates to an outrigger device for wheel-mounted working machines which is so arranged as to minimize its unnecessary vertical projection, its unnecessary extension from the machine width, the amount of projection of the jack cylinder above the machine and to enable the float to be received within the machine width.
2. Description of the Prior Art
These type of outrigger devices are installed with two on each of the front and rear sides of a traveling body, in an H-shaped arrangement as a whole, wherein each outrigger device comprises a fixed box secured to the traveling body, an extensible beam extensibly and storably fitted in said fixed box, and an extensible jack cylinder having a float on the lower end thereof, said jack cylinder being fixed in its vertical position to the front end of said extensible beam.
These types of conventional outrigger devices, however, present the following problems.
These type of wheel-mounted working machines have various restrictions imposed on their body construction because they travel on highways. The limited level of the lower surface of the machine above the ground is one of the restrictions. Thus, the jack cylinder of the outrigger device is required to have an extension stroke which is the sum of said machine level and a stroke for lifting the machine above the ground. For this reason, the overall length of the jack cylinder must be increased and this increase adds to the amount of projection above the machine. Thus, since the jack cylinder projects well above the machine, it interfers with pile driving work, loading work with the truck positioned in close proximity to the machine and other so-called proximity work, thus causing great inconvenience with work. This is the first problem.
Further, to increase the stability of the machine support, it is desirable that the extensible beam project laterally outwardly of the machine as long as possible. For this reason, the jack cylinder is so designed as to minimize its unnecessary vertical projection and unnecessary extension in the direction of the width of the machine. With this design, however, the float mounted on the lower end of the jack cylinder will have its substantially outer half projecting outwardly of the machine width. Thus, it has been common practice to remove the float each time the machine travels on a highway, and the removal of the float has been very troublesome. Further, because of this requirement for mounting and unmounting the float, it has been necessary to reduce the float size in order to reduce the float weight, which is disadvantageous from the standpoint of stability of the machine support.